You could probably fit two CR123's in there, which is the same voltage as 4 AA's. I don't know about current draws, but you should get better performance from 2 Cr123's than 4 AA's.
ALSO: I was reading up on laser units, you could rig one to a CR2032 battery, which is really flat. If you got a 6v laser, you could use 2x CR2032 batteries to power it...
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Ár skal r?*sa, sá er annars vill
fé eða fjör hafa. Sjaldan liggjandi úlfur
lær um getur né sofandi maður sigur.